Research is underway to study how the different types of steroidogenic cells present in the corpus luteum interact to modulate the actions of luteinizing hormone (LH) and prostaglandins F2 alpha (PGF2 alpha) on progesterone secretion. Preliminary evidence suggests that LH acts primarily on a population of small (less than 22 microns in diameter) cells while PGF 2 alpha appears to bind only to large (greater than 22 microns) luteal cells. Research is also underway to ascertain if LH regulates the transport of cholesterol from the cytoplasm into the mitochondria via the action of microfilaments. Studies are in progress to compare the rates of internalization and degradation of LH and human chorionic gonadotropin in cultured ovine luteal cells and to assess the role of the carbohydrate portion of these molecules on these events. The rates of internalization and degradation of low density lipoprotein and epidermal growth factor will be compared to those for human chorionic gonadotropin. Finally, experiments will be conducted to determine if the receptor for LH is degraded or recycled after internalization.